perf(platform-server): speed up resolution of base (#61392)

The `getBaseHref` method is called several times per request and currently queries through the entire document. We can speed it up by taking advantage of the fact that the `<base>` can only be a direct child of the `<head>` and is usually defined towards the beginning. Below are some benchmarks for a "Hello world" app before and after this change.

### Before:
```
Running 60s test @ http://localhost:4202
100 connections with 10 pipelining factor

┌─────────┬────────┬────────┬────────┬────────┬───────────┬──────────┬─────────┐
│ Stat    │ 2.5%   │ 50%    │ 97.5%  │ 99%    │ Avg       │ Stdev    │ Max     │
├─────────┼────────┼────────┼────────┼────────┼───────────┼──────────┼─────────┤
│ Latency │ 568 ms │ 853 ms │ 901 ms │ 904 ms │ 866.58 ms │ 437.6 ms │ 9915 ms │
└─────────┴────────┴────────┴────────┴────────┴───────────┴──────────┴─────────┘
┌───────────┬─────────┬─────────┬─────────┬─────────┬─────────┬─────────┬─────────┐
│ Stat      │ 1%      │ 2.5%    │ 50%     │ 97.5%   │ Avg     │ Stdev   │ Min     │
├───────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ Req/Sec   │ 490     │ 826     │ 1,006   │ 1,643   │ 1,129.3 │ 234.69  │ 490     │
├───────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ Bytes/Sec │ 10.4 MB │ 17.4 MB │ 21.3 MB │ 34.7 MB │ 23.9 MB │ 4.96 MB │ 10.3 MB │
└───────────┴─────────┴─────────┴─────────┴─────────┴─────────┴─────────┴─────────┘

Req/Bytes counts sampled once per second.
# of samples: 60

69k requests in 60.04s, 1.43 GB read
90 errors (90 timeouts)
```

### After

```
Running 60s test @ http://localhost:4202
100 connections with 10 pipelining factor

┌─────────┬────────┬────────┬────────┬─────────┬───────────┬───────────┬─────────┐
│ Stat    │ 2.5%   │ 50%    │ 97.5%  │ 99%     │ Avg       │ Stdev     │ Max     │
├─────────┼────────┼────────┼────────┼─────────┼───────────┼───────────┼─────────┤
│ Latency │ 471 ms │ 831 ms │ 889 ms │ 1668 ms │ 835.91 ms │ 467.89 ms │ 9720 ms │
└─────────┴────────┴────────┴────────┴─────────┴───────────┴───────────┴─────────┘
┌───────────┬─────────┬─────────┬─────────┬─────────┬──────────┬────────┬─────────┐
│ Stat      │ 1%      │ 2.5%    │ 50%     │ 97.5%   │ Avg      │ Stdev  │ Min     │
├───────────┼─────────┼─────────┼─────────┼─────────┼──────────┼────────┼─────────┤
│ Req/Sec   │ 390     │ 860     │ 1,145   │ 1,572   │ 1,156.77 │ 222.65 │ 390     │
├───────────┼─────────┼─────────┼─────────┼─────────┼──────────┼────────┼─────────┤
│ Bytes/Sec │ 8.24 MB │ 18.2 MB │ 24.2 MB │ 33.2 MB │ 24.4 MB  │ 4.7 MB │ 8.24 MB │
└───────────┴─────────┴─────────┴─────────┴─────────┴──────────┴────────┴─────────┘

Req/Bytes counts sampled once per second.
# of samples: 60

71k requests in 60.03s, 1.47 GB read
140 errors (140 timeouts)
```

PR Close #61392

packages/platform-browser/src/browser/browser_adapter.ts

@@ -86,7 +86,7 @@ export class BrowserDomAdapter extends DomAdapter {
 
 let baseElement: HTMLElement | null = null;
 function getBaseElementHref(): string | null {
-  baseElement = baseElement || document.querySelector('base');
+  baseElement = baseElement || document.head.querySelector('base');
   return baseElement ? baseElement.getAttribute('href') : null;
 }
 

packages/platform-server/src/domino_adapter.ts

@@ -79,8 +79,24 @@ export class DominoAdapter extends BrowserDomAdapter {
   }
 
   override getBaseHref(doc: Document): string {
-    // TODO(alxhub): Need relative path logic from BrowserDomAdapter here?
-    return doc.documentElement!.querySelector('base')?.getAttribute('href') || '';
+    const length = doc.head.children.length;
+
+    // The `<base>` can only be a direct child of `<head>` so we can save some
+    // execution time by looking through them directly instead of querying for it.
+    // See: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/base
+    // Note that we can't cache the `href` value itself, because this method gets called with a
+    // different document every time which means that in theory the value can be different too.
+    for (let i = 0; i < length; i++) {
+      const child = doc.head.children[i];
+
+      // Tag names are always uppercase for HTML nodes.
+      if (child.tagName === 'BASE') {
+        // TODO(alxhub): Need relative path logic from BrowserDomAdapter here?
+        return child.getAttribute('href') || '';
+      }
+    }
+
+    return '';
   }
 
   override dispatchEvent(el: Node, evt: any) {